Sheet metal roofing systems of the type to which this invention relates are customarily formed of a series of elongated sheet metal roofing panels or pans of up to one-hundred feet or so in length mounted on a roof substrate in side-by-side relation and joined together at their adjacent longitudinal side edges by a so called standing seam type water-tight joint. The roofing panels are made of either low carbon steel or stainless steel sheet metal of generally channel-shaped form each comprising a flat base portion provided along its opposite longitudinal side edges with upstanding side edge or wall portions one of which is formed at its top with an inturned horizontal top flange portion and the other one of which is formed at its top with an outturned horizontal top flange portion terminating in a downturned edge flange.
In assembling the roofing panels together onto the roof substrate, they are successively placed side-by-side, with their upstanding side edge wall portions adjacent one another and with the outturned horizontal top or seam forming flange portion of one roofing panel overlying and lying against the inturned horizontal top flange portion of the adjacent roofing panel. The downturned edge portion of the outturned top flange portion of the one roofing panel is then bent or folded inwardly around the underside of the inturned top flange portion of the adjacent other one of the roofing panels to engage thereagainst, and the resulting combined assembly of the inturned flange portion and the outturned flange portion with its inturned edge flange then bent downwardly to a vertical position and pressed together with the adjacent upstanding side wall of the other one of the roofing panels to form a folded standing seam joint between the adjoining roof panels.
To fix the joined together assembly of roofing panels down in place onto the roof substrate, sheet metal cleat members, each comprising a vertically extending web portion provided at its top and bottom edges with horizontally outturned flange portions, is customarily interposed between the adjacent upstanding side wall portions of adjacent roof panels, with the top flange portion clamped in place within the folded standing seam joint and the bottom flange portion underlying one of the roofing panels and suitably fixedly attached to the roof substrate as by fastening nails for instance. The cleat members preferably extend continuously the full length of the roofing panels.
To render the folded standing seam joint water-tight and the roof assembly thus suitable for roofs having little or no slope or pitch, a gasket arrangement is preferably provided within the folded standing seam. The gasket arrangement may be comprised of a suitable gasket material which is applied either to the top flange portion of at least one of the upstanding adjacent side edge wall portions of the adjacent roofing panels or to only the seam forming section of the vertical web portion of the cleat member and which is deformable, when the seam is pressed together in a press fit type manner, to form a water-tight seal within the standing seam joint. The gasket material preferably is the terneplate coating described in Federal Specification QQ-T-201F published Nov. 12, 1986 by the United States Government and comprised of an alloy containing about twenty percent tin and eighty percent lead.
A roof system of the above-described type is disclosed in U.S. patent application Ser. No. 415,554 filed Oct. 2, 1989 and assigned to the assignee of the present application. Because of the fixation of the cleat members of such prior roof cladding assemblies at their bottom flange portions to the roof substrate by fastening nails or the like, the adjacent roofing panels which are joined and longitudinally locked together with the cleat members by their standing seam joints are prevented from freely expanding and contracting longitudinally relative to the roof substrate under the varying ambient temperature or weather conditions, such as ice and snow present on the roof structure, to which they are normally subjected. As a result, the expansion and contraction forces exerted by the seamed together roofing panels on the associated cleat member joined thereto within the folded standing seam are apt to cause, especially in the case of roofing panels of a length in excess of thirty feet, eventual loosening of the attachment of the cleat member to the roof substrate with accompanying loosening of the roof assembly thereon and even possible separation therefrom. Also, buckling of the roofing panels is possible because of the prevention of free longitudinal thermal expansion and contraction movement of the roofing panels on the roof substrate.